Obama faces unpleasant, but enduring, part of job in memorial speech

President Obama continues to work on speech he will deliver at memorial Wednesday

Like presidents before him, Obama is thrust into role of "mourner-in-chief"

Presidents Reagan, Clinton and Bush all had defining moments amid national grief

Obama, too, has had unpleasant duty before -- after coal mine disaster and Fort Hood

Watch President Obama's speech live at 8 p.m. ET on CNN.com Live. And join Wolf Blitzer and John King on CNN TV, live from Arizona at 8 p.m. ET, with the latest developments, reactions and coverage of the memorial service for the victims of Saturday's tragedy in Arizona.

Washington (CNN) -- President Obama began working Monday night on the speech he will deliver during a memorial service Wednesday for the victims of Saturday's mass shooting in Tucson, Arizona.

White House officials say Obama has determined the broad idea of what he wants to say and is working with his team of speechwriters on drafting his remarks.

According to one White House official, the president will likely continue tweaking the speech throughout the day before his scheduled Wednesday evening remarks.

While the details, tone and length of the speech have not been released, Obama "will devote most of his remarks to memorializing the victims," a White House official said.

"As president of the United States, but also as a father, obviously I'm spending a lot of time just thinking about the families and reaching out to them," Obama said Monday.

Obama will also meet with family members of victims in Tucson, according to a White House official. The official said details are still being worked out on how many families he will meet with and where.

Like many presidents before him, Obama is thrust into the position of "mourner-in-chief" in the face of a national tragedy. President Ronald Reagan was the voice of a nation grieving after the explosion of the space shuttle Challenger in 1986.

"We will never forget them, nor the last time we saw them, this morning, as they prepared for the journey and waved goodbye and 'slipped the surly bonds of earth' to 'touch the face of God,'" Reagan said from the Oval Office.

President Bill Clinton's remarks following the Oklahoma City, Oklahoma, bombing in 1995 were widely praised and were described by many as a defining moment in his presidency.

"Let us let our own children know that we will stand against the forces of fear," Clinton said at the nationally televised memorial service in Oklahoma City. "When there is talk of hatred, let us stand up and talk against it. When there is talk of violence, let us stand up and talk against it. In the face of death, let us honor life."

From his impromptu remarks and rallying cry atop of mound of rubble at ground zero in New York to his memorable speech at Washington's National Cathedral, President George W. Bush faced a similar task of bringing the country together in the aftermath of the attacks of September 11, 2001.

"It is said that adversity introduces us to ourselves. This is true of a nation as well," Bush said. "In this trial, we have been reminded, and the world has seen, that our fellow Americans are generous and kind, resourceful and brave," he said.

This will not be Obama's first time in this unfortunate territory: He spoke after the West Virginia coal mine tragedy in April 2010 and the shooting at Fort Hood in Texas, in which 13 people were killed, in November 2009.

"It may be hard to comprehend the twisted logic that led to this tragedy. But this much we do know -- no faith justifies these murderous and craven acts," Obama said during the Fort Hood memorial service.

As is always the case, the big challenge is striking the right tone, said presidential scholar Stephen Hess.

"He has to give a lovely, passionate memorial statement, a eulogy of grief, of hope perhaps for the future, said Hess, a former adviser to Presidents Gerald Ford and Jimmy Carter. "But it's not a political speech and it has to be carefully stated it's not a political speech.

"It's always a fine line like this. If he chooses to step over the line and talk about things that subsequently can be dissected as political ... then he's made a mistake and he's done a disservice," Hess said. "But that, I think, is unlikely to happen," Hess said.

A federal judge entered a plea of not guilty Monday on behalf of Jared Lee Loughner to three counts of attempted murder in the mass shooting that wounded U.S. Rep. Gabrielle Giffords earlier this month.